Mouth sores

Mouth sores are damaged, inflamed, or irritated areas in or around the mouth. They may appear as ulcers, blisters, cracks, raw patches, or raised spots. Some are painful, while others cause little discomfort.

A mouth sore is a symptom, not a single disease. Common causes include accidentally biting your cheek, irritation from dental work, canker sores, and viral infections. Less often, sores are linked to a medicine, nutritional deficiency, immune condition, or another illness.

Most simple mouth sores heal without leaving a scar. A sore that does not heal, keeps returning, or occurs with other symptoms should be checked.

A mouth sore may begin with tingling, burning, tenderness, or a rough feeling. Eating, drinking, brushing your teeth, or speaking may make it hurt more.

Depending on the cause, you may notice:

• A round or oval ulcer with a pale centre and red edge
• One blister or a cluster of small blisters
• A cut or raw patch beside a sharp tooth or denture
• Cracks at the corners of the mouth
• White patches that may leave a red surface underneath
• Swollen or bleeding gums
• Sores on the lips as well as inside the mouth

Other symptoms can include fever, swollen neck glands, a skin rash, dry mouth, or sores elsewhere on the body. These details can help identify the cause.

Common causes include minor injuries from cheek biting, hot food, braces, dentures, dental treatment, or a sharp tooth. Strong toothpaste, irritating mouthwash, spicy or acidic foods, and tobacco may worsen an already sore area.

Canker sores, also called aphthous ulcers, are small painful ulcers inside the mouth. They are not contagious. Stress, minor injury, hormonal changes, or certain foods may trigger them in some people, although a clear trigger is often not found.

Cold sores are caused by herpes simplex virus. They usually form grouped blisters on or around the lips and can spread through close contact. Some viral illnesses can also cause sores inside the mouth, especially in children.

Less common causes include oral thrush, which is a yeast infection; low iron, vitamin B12, or folate; and inflammatory conditions affecting the digestive system or immune system. Some medicines can cause ulcers, dry mouth, or more serious reactions involving the mouth.

A persistent ulcer, red or white patch, lump, or area of thickening can occasionally be an early sign of mouth cancer. These changes are not usually an emergency, but they need a prompt dental or medical assessment.

Seek emergency help if you have difficulty breathing, cannot swallow your saliva, or develop rapidly increasing swelling of your tongue, lips, mouth, or throat.

Arrange same-day medical care if you cannot drink enough, are passing much less urine, feel unusually drowsy, or have other signs of dehydration. You should also seek urgent advice for mouth sores accompanied by a widespread rash, blistering or peeling skin, eye pain, or sores around the genitals. This is especially important after starting a new medicine.

Contact a clinician promptly if you have a weakened immune system and develop mouth sores with fever or feel generally unwell.

Book a routine appointment with a dentist or clinician if:

• A sore lasts longer than three weeks
• Sores repeatedly return or are becoming more severe
• A denture, brace, filling, or sharp tooth keeps rubbing the area
• You have unexplained weight loss, a neck lump, or trouble swallowing
• There is a lasting red or white patch, lump, or thickened area

A dentist or clinician will ask when the sore started, whether it has happened before, and what makes it better or worse. They may ask about recent illness, medicines, dental work, diet, skin symptoms, and sores elsewhere on your body.

They will examine the sore and the rest of your mouth. The location, number, shape, and appearance often provide useful clues.

Tests are not always needed. If sores are persistent, severe, or recurrent, testing may include a swab, blood tests for nutritional deficiencies or other conditions, or a small tissue sample called a biopsy. A biopsy helps examine cells under a microscope and does not mean that cancer has been found.

Treatment depends on the cause. Simple injuries and canker sores often heal with measures that reduce pain and prevent further irritation.

You can try:

• Rinsing gently with warm salt water, then spitting it out
• Choosing soft, cool foods and drinking enough fluid
• Avoiding spicy, salty, acidic, sharp, or very hot foods
• Using a soft toothbrush and cleaning your mouth gently
• Protecting the area from a rough denture or brace, if possible
• Using non-prescription pain relief as directed on the label

Do not place aspirin directly on a sore. It can damage the mouth lining. Alcohol-containing mouthwash may also sting or irritate the area.

A pharmacist can advise about protective gels, pain-relieving products, or antiseptic rinses. A clinician may prescribe a corticosteroid like prednisone or hydrocortisone mouth treatment for certain inflammatory ulcers. Cold sores may be treated with antiviral medicine, while thrush requires antifungal treatment.

If a medicine may be contributing, do not stop it without medical advice. A clinician can assess whether it should be changed.

A minor injury or canker sore often improves within several days and heals within one to two weeks. Larger ulcers, infections, and sores caused by ongoing irritation may take longer.

Pain should generally ease as the area heals. Continued rubbing from a tooth, brace, or denture can delay recovery. Recurrent sores may need assessment even when each episode heals.

Keep track of when sores appear, how long they last, and any possible triggers. A photograph can help if the sore has healed before your appointment.

Are canker sores and cold sores the same?

No. Canker sores occur inside the mouth and are not contagious. Cold sores are caused by herpes simplex virus, usually appear on or around the lips, and can spread to other people.

Can stress cause mouth sores?

Stress may trigger canker sores in some people, but it is not the only possible cause. Injury, illness, nutritional deficiencies, medicines, and inflammatory conditions can also contribute.

Should I pop a mouth blister?

No. Popping it can increase pain, damage nearby tissue, and introduce infection. Leave it alone and avoid foods or dental appliances that rub against it.

Can mouth sores spread to other people?

It depends on the cause. Canker sores and injury-related ulcers do not spread. Cold sores and some other viral infections can be contagious, particularly while blisters or open sores are present.